1. Technical Field
This invention relates to novel pyrrolidin-2-one derivatives, their use as neuraminidase inhibitors, to pharmaceutical compositions containing these novel compounds useful for the prevention, treatment or amelioration of viral, bacterial and other infections, and to methods of using the compounds. The present invention is also concerned with novel intermediates or precursors for producing the novel pyrrolidin-2-one compounds of the present invention.
2. Background of the Invention
Despite the wealth of the information available, influenza remains a potentially devastating disease of man, lower mammals, and birds. No effective vaccine exists and no cure is available once the infection has been initiated.
Influenza viruses consist of eight pieces of single stranded RNA, packaged in orderly fashion within the virion. Each piece codes for one of the major viral proteins. The replication complex is enclosed with a membrane composed of matrix proteins associated with a lipid bilayer. Embedded in the lipid bilayer are two surface glycoprotein spikes, hemagglutinin (HA) and the enzyme neuraminidase (NA). All of the viral genes have been cloned and the three-dimensional structures of the surface glycoproetins have been determined.
Influenza viruses continually undergo variation in the two surface antigen, HA and NA, toward which neutralizing antibodies are directed. For this reason, vaccines and a subject""s natural immune system have not been very effective. Attention is now being directed to finding other potential antiviral agents acting at other sites of the virion. This invention is directed to novel compounds which are useful in inhibiting the viral surface enzyme NA.
Furthermore, many other organisms carry NA. Many of these NA-possessing organisms are also major pathogens of man and/or mammals, including Vibraeo cholerae, Clostridium perfringes, Streptococcus pneumonia, Arthrobacter sialophilas, and other viruses, such as parainfluenza virus, mumps virus, Newcastle disease virus, fowl plague virus, and Sendai virus. Compounds of this invention are also directed to inhibiting NA of these organisms.
In viruses, NA exists as a tetramer made of four roughly spherical subunits and a centrally-attached stalk containing a hydrophobic region by which it is embedded in the organism""s membrane. Several roles have been suggested for NA. The enzyme catalyzes cleavage of the xcex1-ketosidic linkage between terminal sialic acid and an adjacent sugar residue. Removal of the sialic acid lowers the viscosity and permits access of the virus to the epithelial cells. NA also destroys the HA receptor on the host cell, thus allowing elution of progency virus particles from infected cells. Research indicates that the active site for influenza neuraminidase remains substantially unchanged for the major strains of influenza. For example, a comparison of sequences from influenza A subtypes and influenza B shows conserved residues with crucial structural and functional roles. Even though the sequence homology is only about 30%, many of the catalytic residues are conserved. Furthermore, the three-dimensional structures of influenza A and B neuraminidases have been determined. Superposition of the various structures shows remarkable structural similarity of the active site. Since the active site amino acid residues are conserved in all known influenza. A neuraminidases that have been sequenced so far, an inhibitor that is effective against different strains of influenza A and/or B neuraminidase can be designed based on the three-dimensional structure of a neuraminidase.
In general, the role of NA is thought to be for the mobility of the virus both to and from the site of infections. Compounds that inhibit neuraminidase""s activity may protect a subject from infection and/or cure a subject once infection has set in. It is a further object of this invention to provide a method of using compounds of this invention for preventing, treating and/or curing a viral infection.
Analogs of neuraminic acid, such as 2-deoxy-2,3-didehydro-N-acetylneuraminic acid (DANA) and its derivatives are known to inhibit HA in vitro; however, these compounds are inactive in vivo. Palese and Schulman, in CHEMOPROPHYLAXIS AND VIRUS INFECTION OF THE UPPER RESPIRATORY TRACT, Vol. 1 (J. S. Oxford, Ed.), CRC Press, 1977, at pp. 189-205.
Von Itzstein et al. Describes cyclohexane analogs of xcex1-D-neuraminic acid of the formula 
wherein:
A is O, C or S in Formula (a), and N or C in Formula (b);
R1 is CO2H PO3H2, NO2, SO2H, SO3H, tetrazolyl-, CH2CHO, CHO, or CH(CHO)2; R2 is H, OR6, F, Cl, Br, CN, NHR6, SR6 or CH2X, where X is NHR6 halogen, or OR6;
R3 and R3xe2x80x2 are H, CN, NHR6, SR6, xe2x95x90NOR6, OR6, guanidino, NR6;
R4 is NHR6, SR6, OR6, CO2R6, NO2, C(R6)3, CH2CO2R6, CH2 or CH2NHR6;
R5 is CH2YR6, CHYR6CH2YR6 or CHYR6CHYR6CH2YR6;
R6 is H, acyl, alkyl, allyl, or aryl;
Y is O, S, NH, or H;
and pharmaceutical salts thereof, useful as antiviral agents.
In addition, certain benzene derivatives are suggested in U.S. Pat. No. 5,453,533 as being inhibitors of influenza virus neuraminidase and various others are disclosed in U.S. patent application ser. No. 08/413,886. Yamamoto et al. Describe various sialic acid isomers as having inhibitory activity against neuraminidase in Synthesis of Sialic Acid Isomers Inhibitory Activity Against Neuraminidase, TETRAHEDRON LETTERS, Vol. 33, No. 39, pp. 5791-5794, 1992.
U.S. Pat. No. 5,512,596 and WO 96/26933 to Gilead Sciences, Inc. describes certain 6-membered ring compounds as possible inhibitors of neuraminidase.
Hoff, et al. Suggests that certain N-aryl xcex1-pyrrolidinones are useful as intermediates for dyes and pharmaceuticals, as reported in Chemical Abstracts, Vol. 52, Item 11124 g, 1958.
However, none of these references disclose the novel pyrrolidin-2-one derivatives of the present invention.
An aspect of the present invention is directed to compounds represented by the formula: 
wherein
Q is CO2H, SO3H, PO3H2, NO2 or esters thereof; 
T is H, OH or OH2 
n is 0-3;
X is (CH2)n, (CH2)nNH, (CH2)nO or (CH2)nS;
Each of R1 and R2 individually is H, (CH2)mA, or (CH2)mZ, and R1 and R2 can be the same or different;
Each of R6 and R7 individually is H, (CH2)mA, or (CH2)mZ, and R6 and R7 can be the same or different;
m is 1-3; 
each of R3, R4 R5 individually is H, lower alkyl, branched alkyl, cycloalkyl, aryl or alkaryl, and R3, R4 and R5 can be the same as or can differ from each other; and pharmaceutically acceptable salts thereof.
The present invention is also concerned with compositions for inhibiting influenza virus neuraminidase comprising a pharmaceutically acceptable carrier and an amount effective for inhibiting influenza virus neuraminidase of a compound as defined above.
A further aspect of the present invention involves a method for inhibiting influenza virus that comprises administering to a patient in need thereof a compound as defined above in an amount effective for inhibiting influenza virus neuraminidase.
A still further aspect of the present invention is concerned with preventing and treating influenza virus infection comprising administering to a patient in need thereof a compound as defined above in an amount effective for inhibiting influenza virus neuraminidase.
The present invention is also concerned with methods for producing the compounds defined above.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described only the preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive.
An aspect of the present invention is directed to compounds represented by the formula: 
wherein
Q is CO2H, SO3H, PO3H2, NO2 or esters thereof; 
T is H, OH or OH2 
n is 0-3;
X is (CH2)n, (CH2)nNH, (CH2)nO or (CH2)nS;
Each of R1 and R2 individually is H, (CH2)mA, or (CH2)mZ, and R1 and R2 can be the same or different;
Each of R6 and R7 individually is H, (CH2)mA, or (CH2)mZ, and R6 and R7 can be the same or different; m is 1-3; 
each of R3, R4 R5 individually is H, lower alkyl, branched alkyl, cycloalkyl, aryl or alkaryl, and R3, R4 and R5 can be the same as or can differ from each other; and pharmaceutically acceptable salts thereof.
The esters are typically lower alkyl esters having 1 to about 12 carbon atoms and preferably 1 to about 3 carbon atoms and aryl esters containing 6 to 14 carbon atoms. The alkyl esters can be straight-chain, branched-chain or cyclic saturated aliphatic hydrocarbons.
Examples of some alkyl esters are methyl, ethyl, propyl, isopropyl, t-butyl, cyclopentyl and cyclohexyl esters. The aryl esters are preferably phenyl or alkyl substituted aromatic esters (alkaryl) including C1-3 alkyl substituted phenyl such as benzyl.
The alkyl groups contain 1 to about 12 carbon, and preferably 1 to about 3 carbon atoms, and can be straight, branched-chain or cyclic saturated aliphatic hydrocarbon groups.
Examples of suitable alkyl groups include methyl, ethyl and propyl. Examples of branched alkyl groups include isopropyl and t-butyl. Examples of suitable cyclic aliphatic groups typically contain 3-8 carbon atoms and include cyclopentyl and cyclohexyl.
Examples of substituted cycloalkyl groups include cyclic aliphatic groups typically containing 3-8 carbon atoms in the ring substituted with alkyl groups typically having 1-6 carbon atoms and/or hydroxy group. Usually 1 or 2 substituted groups are present.
Examples of aryl groups are phenyl and naphthyl. Alkaryl groups typically contain 1-3 carbon atoms in the alkyl group such as benzyl. The alkyl moiety can be linear or branched.
Pharmaceutically acceptable salts of the compounds of formula (I) include those derived from pharmaceutically acceptable, inorganic and organic acids and bases. Examples of suitable acids include hydrochloric, hydrobromic, sulphuric, nitric, perchloric, fumaric, maleic, phosphoric, glycollic, lactic, salicyclic, succinic, toluene-p-sulphonic, tartaric, acetic, citric, methanesulphonic, formic, benzoic, malonic, naphthalene-2-sulphonic, trifluoroacetic and benzenesulphonic acids.
Salts derived from appropriate bases include alkali such as sodium and ammonia.
Examples of some specific compounds within the scope of the present invention are:
1-{2-{[(Amino)(imino)methyl]amino}-4-carboxyphenyl}pyrrolidin-2-one;
1-{2-{[(Amino)(imino)methyl]amino}-4-carboxyphenyl }-5-(hydroxymethyl)pyrrolidin-2-one;
1-{2-{[(Amino)(imino)methyl]amino}-4-carboxyphenyl}-5-(aminomethyl)pyrrolidin-2-one;
1-(4-Carboxyphenyl)-5,5-bis-(hydroxymethyl)pyrrolidin-2-one;
1-{2-{[(Amino)(imino)methyl]amino}-4-carboxyphenyl}-5,5-bis-(hydroxymethyl)pyrrolidin-2-one;
1-{4-Carboxy-2-(3-pentylamino)phenyl]pyrrolidin-2-one;
1-[4-Carboxy-2-(3-pentylamino)phenyl]-5,5-bis-(hydroxymethyl)pynolidin-2-one;
1-[4-Carboxy-2-(3-hexylamino)phenyl]-5,5-bis-(hydroxymethyl)pyrrolidin-2-one;
1-[4-Carboxy-2-(4-heptylamino)phenyl]-5,5-bis-(hydroxymethyl)pyrrolidin-2-one;
1-{4-Carboxy-2-[(3-pentyl)methylamino)phenyl}-5,5-bis-(hydroxymethyl)pyrrolidin-2-one;
1-[4-Carboxy-2-(propylamino)phenyl]-5,5-bis-(hydroxymethyl)pyrrolidin-2-one;
1-[4-Carboxy-2-(pentylamino)phenyl]-5,5-bis-(hydroxymethyl)pyrrolidin-2-one;
1-[4-Carboxy-2-(ethylcarbonylamino)phenyl]-5,5-bis-(hydroxymethyl)pyrrolidin-2-one;
1-{[4-Carboxyl-2-(1-methylpropylcarbonylamino)phenyl}-5,5-bis-(hydroxymethyl)-pyrrolidin-2-one;
1-{[4-Carboxyl-2-(1-ethylpropyl)carbonylamino]phenyl}-5,5-bis-(hydroxymethyl)-pyrrolidin-2-one;
5-Aminomethyl-1-{[4-carboxy-2-(1-methylpropyl)carbonylamino]phenyl}-5-bis-hydroxymethylpyrrolidin-2-one; and
1-[4-Carboxyl-2-(1-ethylpropylamino)phenyl]-5-hydroxyethyl-5-hydroxymethyl-pyrrolidin-2-one;
Specific example of suitable compounds also include compound A, the ethyl ester derivative of example 8 shown below: 
Another compound B contains an amino group in place of hydroxyl, and the structure is shown below: 
This compound was approximately twice as effective as example 8 for the inhibition of influenza neuraminidase (N2), as summarized in the Table below. This is surprising and noteworthy activity for the new compound.
Another compound is the ethyl ester derivative of Compound B, which may serve as a potential prodrug. Since Compound C is an amino acid that will be charged at all pH values, this ester derivative provides a possible prodrug form that may be more bioavailable but, once absorbed into the blood, could be acted upon by plasma or liver esterases to release the active amino acid form. The structure of Compound A is shown below: 
A ring-expanded homolog of example 8 is shown below as Formula (II): 
Where R=OH, NH2, or guanidine.
Another compound contains a phenolic ether side chain in combination with a fourth, hydrogen bonding substituent on the benzene ring, and the structure is shown below as formula (III): 
Where Y is H, OH, NH2, or guanidine, and R is OH, NH2, or guanidine.
An additional compound contains a benzylic alcohol or amine (or its guanidine derivative) in combination with a branched hydrophobic grouping, and the structure is illustrated below as formula (IV): 
Where R1=H, OH, NH2, or guanidine, and R2=OH, NH2, or guanmdine.
Other components include a sulfur analog of example 8. The structure is shown below as formula (V): 
Where R is OH, NH2, or guanidine.
Yet another compound include aliphatic hydrophobic groupings in combination with a fourth hydrogen bonding substituent on the benzene ring. The general structure for these components is illustrated below as formula (VI): 
Where R1 is CH2CH(CH2CH3)2 or CHxe2x95x90C(CH2CH3)2, R2 is OH, NH2, or guanidine, and Y is H, OH, NH2, or guanidine.
Finally, extra interactions can be generated between the ligand and protein binding site by extending the side chains from the pyrrolidinone ring. The structure of group of components is illustrated below as formula (VII): 
Where X is CH2, O, NH, CH(OH), or CH(NH2), Y is H, OH, NH2, or guanidine, R1 is OH, NH2, or guanidine, and R2 is H, OH, NH2, or guanidine, and R3 is a linear or branched alkyl group from 2-8 carbons.
The compounds of the present invention can be prepared by methods illustrated in the following schemes. 
14, R3=C2H5; 15, R3=CH(CH3)C2H5; 16, R3=CH(C2H5)2